wp-includes/class-wp-theme-json.php:695Returns a class name by an element name.
$elementstringstring public static function get_element_class_name( $element ) { $class_name = ''; if ( isset( static::__EXPERIMENTAL_ELEMENT_CLASS_NAMES[ $element ] ) ) { $class_name = static::__EXPERIMENTAL_ELEMENT_CLASS_NAMES[ $element ]; } return $class_name; }Introduced in 6.1.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wp-theme-json.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.